When backing up the other day really easy all of a sudden the truck stopped and a grinding noise started the truck still drives forward but wont back up, just grinds tried shifting the transfer but still nothing the drive shaft wont turn

A grinding or rumbling noise can also be symptoms of a wheel bearing or constant velocity joint in a driveshaft. A worn wheel bearing can also cause a 'whistling' sound (as can a worn CV joint).

A grinding noise with brakes is either worn pads causing metal to metal contact on the brake disk/rotor, or the brake backing plate catching on a spinning rotor ... or a loose/missing anti squeal brake shim (they stop the pads from rattling and vibrating).

However, as you say a mechanic has looked at the brakes and can't find anything wrong .. I think I would begin to suspect a wheel bearing or constant velocity joint on the driveshaft (front wheel drive cars).

sounds like rear end is coming apart
google wrangler forums and post there

Failed Transmission Again

Part with it

Get something else

Maybe American (Rear Wheel Drive Only)

If it is an automatic transmission, first check the fluid level. If it is low, fill it up and try it again. If the level is fine, then there is a bigger issue and you should seek a professional's help.

throw out bearing or worn clutch

sounds like a bad throw out bearing you have to take the tranny out to replace it.

Flex plate is cracked. That is another reason it stalls.

i would say your transfer case is on its way out. but it is hard to say that is a lot of info to take in but ya i say tranfer case is toste

Have your rear brakes checked. It might be a brake wear indicator. Or your rear brakes are stuck on the brake drum.

THIS IS 2 LITTLE PLASTIC TABS ON THE FORK IN THE TRANSFER CASE.